The present invention relates to a ceramic fiber yarn, and a method of and a spinning machine for making the same, more precisely relates to a ceramic fiber yarn, whose crystal structure of filaments substantially changes to polycrystalline mullite after heating at high temperature, and a method of and a spinning machine for making the same.
Since ceramic fiber yarns, e.g., alumina, have a superior heat-resisting property, they are widely used for anti-heat products. For example, conventional ceramic yarns disclosed in the U.S. Pat. No. 4,047,965 have a crystal structure of polycrystalline transition alumina, so the crystal structure of their filaments changes to polycrystalline mullite when they are heated at high temperature. Therefore, at high temperature, the ceramic yarns have higher flexibility than ceramic yarns which has .alpha.-alumina crystals after heating at high temperature. By having the higher flexibility at high temperature, cloth made of the ceramic yarns disclosed in said US patent are used for a lining of furnaces, etc..
Since the conventional yarns are made from mother liquid, which substantially includes no chlorides, the yarns include substantially no chlorine. If yarns are made from mother liquid including chrolide, such as basic aluminum chloride, the weaving and knitting performance is lowered, and fluff is apt to be formed.
On the other hand, the mother liquid including chlorides has higher extensibility, so that the productivity of the yarns can be raised. If the mother liquid, which includes water-dispersible alumina sols or water-soluble organic aluminum salts instead of basic aluminum chloride, is used, the extensiblity and productivity of yarns will be lower than that of yarns which are made from mother liquid including basic aluminum chloride.